Air pressure intensifier for hydraulically operated pressure pads



April 19, 1960 F. M. WILLIAMSON ,307

AIR PRESSURE INTENSIF'IER FOR HYDRAULICALLY OPERATED PRESSURE PADS Filed Feb. 16. 1959 E: a v4; I INVENTOR.

EYE-I'- V E. '3 ifyJ/fM/Zkz/sd?! United StatesPatent AIR PRESSURE INTENSIFIER FOR HYDRAULI- CALLY OPERATED PRESSURE PADS Floyd M. Williamson, Detroit, Mich. Application February 16, 1959, Serial No. 793,499

12 Claims. (Cl. 267-1) This invention relates to presses employing a hydraulic cushion for the die pads and has particular reference to a' hydraulic system actuated by a relatively low pressure air supply and incorporating means actuated: by the operation of the press for increasing the air pressure sub stantially above that at which it is supplied to the 'sys-' tank of the hydraulic system is partially filled with oil and pressurized from a normal shop air line developing Such air pressure forces the oil in the system througha valve unit" 75 to 100 pounds per square inch pressure.

to the hydraulic cushion reacting on the pressure pad inthe die, the force exerted by such hydraulic cushion being proportional to the pressure in the supply tank."

The pressured pad is used to hold a workpiece in the die :and is moved down with the press ram as the press closes, the cushion being operable for returning the pad to its upper position as the press ram moves upwardly on the" opening of the press. The pad in returning to its upper position strips the part from the die or punch after being: formed. The forming or punching operation is performed by the pressure of the press ram forcing the workpiece held in place by the pressure pad into the die and forcing the pad down with the part. When the press ram retracts upon the opening of thepress, the pressure pad under the influence of the hydraulic cushion is forced back to its original position lifting the workpiece from the die. The lifting pressure exerted on the die pad when .the hydraulic system is energized by the usual shop air The invention conline is not sufficient in many cases. templates a meansfor utilizing the force developed by .the closing of the press to increase the pressure of the vair in the supply tank and thus provides sufiicient pres- :.Sl.1IB in the hydraulic cushion for stripping the work from .the lower die.

A principal object of the invention, therefore, is to ;provide an air pressure intensifier for hydraulically op- .e'rated pressure pads.

Other and further objects of the invention will be apparent from the following description and claims and may be understood by reference to the accompanying drawing, which by Way of illustration shows preferred embodiments of the invention and what I now consider.

to be the best mode of applying the principles thereof. Other embodiments of the invention may be used withoutdeparrting from the scope of the present invention .as set forth in the appended claims.

2,933,307 Patented Ap:r'.' 19,' med In the drawing:

Figure 1 is a schematic view of a hydraulically operat ed pressure pad system incorporating my invention;

Figure 2 is a schematic view illustrating a. modified form of the invention; and

Figure 3 is a view of the air pressure booster of Figure 2, shown in another position.

As illustrated in Figure l, a ram type press 10 includes a reciprocable upper die 12 and a lower die comprising a fixed section 14 and areciprocable pad 16. The sec: tion 14 is fixed to be bolster 18 while the pad 16 is biased upwardly to the position as shown by a hydraulic cushion which includes a cylinder 20 and a piston 22, the piston 22 being arranged to react on the, pad 16 so as to resist downward movement thereof by the upper die section 12 during closing of the press and to move the pad upwardly to the position illustrated upon opening of the press. Hydraulic fluid under pressure is supplied to the cylin der 20 from a tank 24 through a line indicated generally at 26 which includes conduit 28'between the tank- 24 and the valve unit 30, passage 32 through the valvereturn flow of hydraulic fluid from the passage 32 intothe conduit 28. A spring pressed check valve 38 is arranged at the discharge end of the conduit 32 so as to: prevent return flow of hydraulic fluid from the conduit 34 into the passage 32 through the discharge end thereof. The tank 24 contains a supply of hydraulic fluid, such as oil 46. An adjustable pressure relief valve 42 connected with the upper end of the tank 24 provides a means for limiting the-maximum pressure inside the tank 24. Air under low" pressure; say for example pounds per square inch, is supplied through an air pressure line "44. past an adjustable pressure regulating valve 46 andfa" check valve 48 to the air cylinder 50, and from the cylin-i der 50 air under pressure may flow through the air.

pressure line 52 to the upper end of the tank 24. Check valve 54 in the air line 52 prevents back flow of air. under pressure from the tank 24 to the cylinder50. I Thus. air under the pressure regulated by the valve 46 will be supplied to the upper end 10f the tank 24 and will. pres surize the oil 40 in the tank 24, the conduit 26, and the cylinder 20. p p i p Upon closing of the press, the upper die 12 will react on the pad 16 and the piston 22, moving the same down; wardly, thereby displacing oil from the cylinder 20 into' conduit 34. The check valve 38 prevents return flow of oil from the conduit 34 into the conduit 32. .However, an adjustable pressure relief valve 56 arranged in a by; pass 58 around the check valve 38 permits return flow of oil from the conduit 34 into the passage 32 when the pressure for which the valve 56 is set is exceeded, which occurs during closing of the press. The valve 56 is set so as to develop sufficient resistance to displacement of oil from the cylinder 20 so that the piston 22 will provide a hydraulic cushion for the pad 16. 'A by-pass 60 having an adjustable safety relief valve 62 therein is" adapted to permit flow of oil from the passage 32 into" the passage 28 around the check valve 36 when the pressure in the passage 32 exceeds that for which the valve 62 is set.

A passage 64 in the valve 30 intersects the passage 32' and at one end communicates with the valve 62 and at its other end with the discharge end of a hydraulic cylinder 66 having a piston 68 therein. The piston 68 is. connected to a piston 70 which is operatively disposed in the air cylinder 50, and a spring 72 biases the pistons 68 and 70 to their advanced positions. The etfective aosaaor area of the piston 70 is many times (say, for example, ten times) that of the piston 68. A by-pass conduit'M extends between the tank 24 and the cylinder 66 at a point remote from the discharge end thereof, and the piston 68 will function as a valve to close the by-pass conduit 74.

Assume that the hydraulic system, including the tank 24, is charged with oil, that the pistons 68 and 70 are in their advanced positions, and that the pressure relief valve 62 is set at a substantially higher pressure than that of the valve 56. Upon closing of the press the hydraulic cushion formed by the piston 22 and cylinder .26 will react on the padj16 to resist downward movement thereof by the die 12. However, when the pressure in the line 34 exceeds that for which the valve 56 is set, thevalve 56 will open and permit the flow of oil under pressure from the line 34 into the line 32 and into the cylinder 66, causing the piston .68 to retract against the air pressure in the cylinder 50, and permitting return'of .oil through hy-pass 74 to tank 24 so long as the lay-pass 74 is open. Depending upon the resistance to flow through by pass 74, the piston 68 may move upwardly past the by-pass 74 due to the surge of fluid under pressure in passage '32 during closing of the press. When the air piston 7!) is forced up, air in the cylinder 50' is forced through the line 52 past the check valve 54 into the tank 24, thus increasing the air volume and pressure in the tank by a small amount.

Upon opening of the press, the upward movement of the die 12 away from the pad 16 will release the pressure in "the line '34 and cylinder 20, whereupon oil under pressure from the tank .24 will flow through the line 26,

thereby upwardly displacing the piston 22 in the cylinder .20 and moving the pad 16 upwardly. Since the piston 68 is under the pressure of the air in the air cylinder 50, some oil will also flow from the cylinder 66 into the passage 32 at such time. Thus upon each closing of thejpress the pistons and 70 move upwardly, thereby displacing a small amountIof .air from the cylinder :50

through the line 52 to the upper part of the tank 24, thereby increasing the pressure of the air in the upper end of the tank 24. It will thus be evident that as the press continues to operate, the air pressure in the tank 24 will increase to a value substantially in excess of that atwhich air under pressure issupplied through the line 44. As previously noted, valve 42 will limit thepressure developedinthe tank 24.

'In the modification .of Figures .2 and v3, the hydraulic fluidlline 26 from the tank 24 to the cylinder 20 is the same as'in'Figure 1, except that the check valve 38 and thepressure relief valves 5.6 and 62 are omitted. Thus upon the closing of the press as shown in Figure 2, the surge .of pressure fluid in the conduit 34 is transmitted to the cylinder 66 in which the piston 168 is reciprocable. Inthis case the cylinder 66 and the air cylinder 50 are the same size, as are the air piston 170 and the hydraulic piston1'68. Thus the air under pressure in the air cylinder50 plus the force of the spring 172 reacting on the piston 168 resist the downward movement of the piston 22. However, the downward movement of the piston 22 upon the closing of the press will force fluid into the cylinder 66, therebyupwardly moving-the piston 168 and displacing air under 'pressure'f-rom the cylinder 50 past the check valve 54Land through theline 52 to a the: pressure tank 24. When the piston 168 moves above the end of the by-pass'74,'the excessfluid displaced by 'the downward movement of the piston '22 will be returned to the tank 24 through the by-pass 74. The construction-and operation of the modification of Figures Z'Eand '3 areotherwisethe same as in Figure 1.

"While I have illustrated and described preferred embodiments'of my invention, it is understood that these are capable of modification, and I therefore do not wish to belimited to the precise details set forth but idesire tothe purview of the following claims;

I claim:

1. In a ram press having a movable pressure pad arranged to be moved in one direction by the press ram upon the closing of the press and a hydraulic cushion reacting on said pad to resist such movement and to move such pad in the other direction upon the opening of the press; a tank of hydraulic fluid, an air pressure line connected to said tank for subjecting fluid therein to pressure, a hydraulic line extending from said tank to said cushion for supplying hydraulic fluid under the pressure in said tank to said cushion, an air pressure booster including an air cylinder having a piston therein and a hydraulic cylinder having a piston therein, said pistons being interconnected formovementtogether and said air piston having an effective area much greater than the hydraulic piston connected thereto, the discharge end of Said hydrau i cyl nde be ng connected to said h drau line, a check alve in sai hyd au l n w en sa d tank and said hydraulic cylinder, a check valve in said hydraulic line between said hydraulic cylinder and said cushion, and a pressure relief valve controlled byapass around said last-mentioned check valve, a hydraulic line extending from said tank to said hydraulic cylinder and communicating with said hydraulic cylinder at a point intermediate the ends thereof, said air pressure line connected to said tank being connected to said air cylinder of said booster and having a check valve therein which permitsflow of air from said air cylinder to said tank and a check valve therein to prevent return flow of air under upon the closing of the press and a hydraulic cushion reacting on said pad to resist such movement and to move such pad in the other direction upon theopening of the press; ,said hydraulic cushion including a cylinder and a pis on therein, a tank of hydraulic fluid, an a Pressure line connected t ,said tan for u je ti g th fluid therein to pressure, a hydraulic line extending from said tank to said cylinder for supplying hydraulic fluid under the pressure in said tank to said cylinder whereby the piston therein reacts on said pad, an air pressure booster, including an air cylinder having a piston therein and a hydraulic cylinder having a piston therein, said last-named pistons being interconnected for movement together, the discharge end of, said booster hydraulic cylin'der being connected to said hydraulic line, a checkvalve insaid'hydraulic line between said tank and said booster a hydraulic cylinder, a hydraulic line extending from said tank to. said booster hydraulic cylinder and communicating with said hydraulic cylinder ,at a point intermediate the 7 such pad in the other direction upon the opening of the press; a tankof hydraulic fluid, an air pressure line connected to said tank for subjecting the fluid therein to pressure, a hydraulicrline extending from said tank to said cylinder for supplying hydraulic fluid under the pressure in said tank to said cylinder whereby the piston therein reacts on said pad, an airpressure booster including an air cylinder haying a piston therein and a hydraulic cylinder having a piston therein, said last-named pistons being interconnected for movement together and said air piston having an effective area much greater than the hydraulic piston connectedthereto, the discharge end of said bo'ost'e'r hydraulie cylinder -being*connected to said hydraulic line, a-- check valve in said hydraulic line between said tank and said booster hydraulic cylinder, a hydraulic line extending from'said tank to said booster hydraulic cylinder and communicating with said hydraulic cylinder at a point intermediate the ends thereof, said air pressure line connected to said tank being connected to said air cylinder of said booster and having a check valve therein which permits flow of air from said booster cylinder to said tank and a check valve therein to prevent return flow of air under pressure from said air cylinder through such line.

4. In a ram press having a movable pressure pad arranged to be moved in one direction by the press ram upon the closing of the press and a hydraulic cushion reacting on said pad to resist such movement and to move such pad in the other direction upon the opening of the press; said hydraulic cushion including a cylinder and a piston therein, a tank of hydraulic fluid, an air pressure line connected to said tank for subjecting the fluid therein to pressure, a hydraulic line extending from said tank to said cylinder for supplying hydraulic fluid under the pressure in said tank to said cylinder whereby the piston therein reacts on said pad, an air pressure booster including an air cylinder having a piston therein and a hydraulic cylinder having a piston therein, said lastnamed pistons being interconnected for movement to gether and said air piston having an effective area much greater than the hydraulic piston connected thereto, the discharge end of said booster hydraulic cylinder being connected to said hydraulic line, a check valve in said hydraulic line between said tank and said booster hydraulic cylinder, a check valve between said booster hydraulic cylinder and said cushion cylinder and a pressure relief valve controlled by-pass around said last-mentioned check valve, a hydraulic line extending from said tank to said booster hydraulic cylinder and communicating with said hydraulic cylinder at a point intermediate the ends thereof, said air pressure line connected to said tank being connected to said air cylinder of said booster and having a check valve therein which permits flow of air from said booster cylinder to said tank and a check valve therein to prevent return flow of air from said booster cylinder under pressure through such line.

5. In a ram press having a movable pressure pad arranged to move in one direction by the press ram upon the closing of the press and a hydraulic cushion reacting on said pad to resist such movement to move such pad in the other direction upon the opening of the press, a tank of hydraulic fluid, an air pressure line connected to said tank for subjecting the fluid therein to pressure, a hydraulic line from said tank to said hydraulic cushion for supplying hydraulic fluid under the pressure in said tank to said cushion whereby the cushion reacts on said pad, a check valve in said hydraulic line arranged so that the hydraulic fluid in said cushion is always subject to the pressure in said tank, a pressure relief by-pass around said valve, an air pump, a one-way communication between said air pump and said tank whereby the air discharged by said pump is supplied to said tank, and means responsive to the displacement of hydraulic fluid from said cushion into said hydraulic line for actuating said air pump whereby the air discharged therefrom is effective for increasing the pressure in said tank above the pressure in said air pressure line.

6. In a ram press having a movable pressure pad arranged to be moved in one direction by the press ram upon the closing of the press and a hydraulic cushion reacting on said pad to resist such movement and to move such pad in the other direction upon the opening of the press; a tank of hydraulic fluid under pressure, a hydraulic line extending from said tank to said cushion for supplying hydraulic fluid under the pressure in said tank to said cushion, an air pressure booster including an air cylinder having is pistontherein and 'a hydraulic cylinder having a piston therein, said last-named pistons being interconnected for movement together, the discharge end of said hydraulic; cylinder. being connected to said hydraulic line, a check valve in said hydraulic line between said tank and said hydraulic cylinder, a second hydraulic line extending from said tank to said hydraulic cylinder and communicating with said hydraulic cylinder at a point intermediate the ends thereof, an air pressure line interconnecting said tank and said air cylinder and having a check valve therein which permits flow of air from said air cylinder to said tank, and an air pressure line connected to said air cylinder and having a check valve therein which prevents return flow of air under pressure from said air cylinder through such line.

7. Apparatus according to claim 6 including a pressure relief by-pass around said check valve in said hydraulic line.

8. Apparatus according to claim 6 wherein the eflective area of said pistons is the same.

9. Apparatus according to claim 6 wherein a check valve is arranged in said first mentioned hydraulic line between said hydraulic cylinder and said cushion and a pressure relief by-pass is disposed around said check valve.

10. Apparatus according to claim 6 including a spring reacting on said piston in said hydraulic cylinder for biasing said piston to obstruct the communication of said second hydraulic line with said hydraulic cylinder and wherein said hydraulic cylinder and the piston therein form a pressure relief by-pass around said check valve in said hydraulic line.

11. In a ram press having a movable pressure pad arranged to move in one direction by the press ram upon the closing of the press and a hydraulic cushion reacting on said pad to resist such movement and to move such pad in the other direction upon the opening of the press, a tank of hydraulic fluid under air pressure, a hydraulic line from said tank to said hydraulic cushion for continuously supplying hydraulic fluid under the pressure in said tank to said cushion whereby the cushion reacts on said pad and the hydraulic fluid therein is always subject to the pressure in said tank, a check valve in said line, an air pump actuated by operation of said press, a one way communication between said air pump and said tank whereby the air discharged by said pump is supplied to said tank for increasing the pressure therein, said air pump having a piston which reacts on the hydraulic fluid in said hydraulic line between said check valve and said cushion and forms a part of a pressure relief by-pass around said check valve.

'12. In a ram press having a movable pressure pad arranged to move in one direction by the press ram upon the closing of the press and a hydraulic cushion reacting on said pad to resist such movement and to move such pad in the other direction upon the opening of the press, a tank of hydraulic fluid, an air pressure line connected to said tank for subjecting the fluid therein to pressure, a hydraulic line from said tank to said hydraulic cushion for supplying hydraulic fluid under the pressure in said tank to said cushion whereby the cushion reacts on said pad, a check valve in said hydraulic line arranged so that the hydraulic fluid in said cushion is always subject to the pressure in said tank, a pressure relief by-pass around said valve, and an air pump actuated by the hydraulic fluid displaced from said cushion by operation of said press and connected to said air pressure line and tank for increasing the pressure in said tank above the pressure in said air pressure line, said air pump forming part of a hydraulically actuated booster which includes a hydraulic cylinder having a piston therein connected to said air pump for operating the same, said booster hydraulic cylinder having its discharge end connected to said hydraulic line between said check valve and cushion References Cited in the file of this patent 5 UNl E ST TE A E TS 1,354,785 .St-rand Oct. 5, 1920 TFQREIGN PATENTS Gr at Britain Man 19 1 

